Grating or screen for photomechanical printing processes.



Nu.'680,928. l Patented Aug. 20, 190i. M. ILEW.

GBATING 0R SCREEN FUR PHUTUMEGHAMCAL PRINTING PRHESSES.A

(Application led Duc. 1 1. 1900A (No Model.)

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MAX LEVY, OF PHILADELPHIA, PENNSYLVANIA.

GRATING 0R SCREEN FOR PHOTOMECHANICAL PRINTING PROCESSES.

SPECIFICATION forming part Of Letters Patent No. 680,928, dated August20, 1901.

Application filed December 1l, 1900. Serial No. 39,547. (No model.)

To @ZZ whom t may conce-7%.-

Be it known that I, MAX LEVY, a citizen of the United States, residingat Philadelphia, in the county of Philadelphia and State ofPennsylvania, have invented new and useful Improvements in Gratings orScreens for Photomechanical Printing Processes, of which the followingis a specification.

This invention relates to improvements in gratings or screens such asare used in the production of half-tone photomechanical engravings; andthe invention consists more particularly in the means employed forsecuring together the prepared or ruled plates of glass.

In carrying out the invention I use two lined or ruled plates of glass,the smaller plate having beveled edges, which plates are held togetherby strips of glass secured to the projecting edges of the larger plateand to the beveled edges of the smaller plate by means of cement,whereby objections incident to the old ways of connecting the plates areobviated.

In the accompanying drawings, Figure lis a sectional view of a gratingconstructed in accord with my invention; Fig. 2, a plan view of aportion of a grating; and Fig. 3, a perspective view showing a portionof a grating, the retaining-strip being separated from the ruled plates.

In carrying out my invention one of the lined or ruled plates of glass Ahas a beveled edge and is smaller than the other lined or ruled plate B,to which it is secured by strips of glass C, which may be of lessthickness than the plate A, the edge c of the strip being beveled toconform to the beveled edges of the plate A. The beveled edges of theplate A and the strips C are preferably ground, and the portion of theplate B which extends beyond the plate A may also be ground or otherwiseroughened. The lined platesA and B may be connected by Canada balsam,and the strips C are cemented to the beveled edges of the smaller plateand to the projecting portion of the larger plate by means of a cementd, which has as its base'soluble glass (silicate of sodium) and powderedasbestos, to which may be added a coloring-matter when it is desired toprovide the grating with a colored border. The amount and character ofthe cement preclude the possibility of acid or moisture getting betweenthe ruled plates.

I-Ieretofore it has been customary to seal two plates of the same sizeone upon the other with Canada balsam and grind the edges or to bind theruled plates together with some form of adhesive tape. Where the edgesof the two plates are simply ground and left in that condition there aremany factors which tend to cause the two plates of glass to separate atthe edges, which allows the silver solution that drains from thesensitized plate used in connection, with the grating and adjacent tothe same to find its way between the plates of glass. If the edges arebound with adhesive tape, the difculty mentioned is to some extentobviated; but the use of tape is objectionable, as the overlyingportions of the same are in the way when cleaning the surfaces of thescreen and, being constantly subject to abrasion in polishing, thescreen soon deteriorates.

The beveled edges of the plate A and the strip are etched or ground toprovide roughened surfaces,to which'the cement will adhere, and, ifdesirable, the inner face of the strip may be roughened as Well as thatportion of the plate B which projects beyond the smaller plate. Wherethe lines or rulings are cut or etched into the plates, a roughenedsurface will be present and it Will not be necessary to abrade theborder of the larger plate.; but where the rulings do not extend belowthe surface of the glass the polished face next to the protectivebordering-strip may be roughened by grinding or etching.

In practice the thickness of the glass bordering-strip may be slightlyless than the thickness of the top plate, so that the cement CZ willbring the surface of the strip substantially on a line with the surfaceof the top plate, though in practice the surface of the glass strips Cmay be slightly below the surface of the plate with beveled edges. Thestrips may be mitered at their ends, and the cement, especially whencolored, shows through the glass strip and the project-ing portion ofthe larger plate, giving to the completed grating an ornamentalappearance.

I claiml. A grating or screen for use in the pro duction of half-tonephotomechanical engravings made up of lined plates of different sizes,the smaller plate having beveled edges, strips with beveled edgescemented to the larger plate and to the beveled edges of the smallerplate.

2. A grating or screen for use in the production of half-tonephotomechanical en gravings, consisting of lined plates of differentdimensions the smaller plate being centered upon the larger plate andprovided with beveled edges, strips with beveled or undercut edges whichare cemented to the projecting portions of the larger plate and to thebeveled edges of the smaller plate, substantially as shown.

3. A grating or screen for the purpose set

